Modeling of intervertebral discs.

A model with rotational symmetry of an intervertebral disc is studied. The nucleus pulposus is assumed to consist of an incompressible fluid, and the annulus fibrosus is modeled by 11 fiber layers with alternating fiber inclination. The spaces between the fiber layers are assumed to be filled with an incompressible fluid. The pressures in the fluid compartments, the fiber strains, and the bulge are calculated under different assumptions regarding fiber inclination, fiber force-elongation relation, initial fiber layer bulges, and so on. The agreement with experimental results is very good. Possible extensions of the model are briefly discussed.